The patch below does not apply to the 3.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bb61b843ffd46978d7ca5095453e572714934eeb Mon Sep 17 00:00:00 2001

From: Vaibhav Jain vaibhav@linux.ibm.com Date: Wed, 30 Jan 2019 17:56:51 +0530 Subject: [PATCH] scsi: cxlflash: Prevent deadlock when adapter probe fails

Presently when an error is encountered during probe of the cxlflash adapter, a deadlock is seen with cpu thread stuck inside cxlflash_remove(). Below is the trace of the deadlock as logged by khungtaskd:

cxlflash 0006:00:00.0: cxlflash_probe: init_afu failed rc=-16 INFO: task kworker/80:1:890 blocked for more than 120 seconds. Not tainted 5.0.0-rc4-capi2-kexec+ #2 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/80:1 D 0 890 2 0x00000808 Workqueue: events work_for_cpu_fn

Call Trace: 0x4d72136320 (unreliable) __switch_to+0x2cc/0x460 __schedule+0x2bc/0xac0 schedule+0x40/0xb0 cxlflash_remove+0xec/0x640 [cxlflash] cxlflash_probe+0x370/0x8f0 [cxlflash] local_pci_probe+0x6c/0x140 work_for_cpu_fn+0x38/0x60 process_one_work+0x260/0x530 worker_thread+0x280/0x5d0 kthread+0x1a8/0x1b0 ret_from_kernel_thread+0x5c/0x80 INFO: task systemd-udevd:5160 blocked for more than 120 seconds.

The deadlock occurs as cxlflash_remove() is called from cxlflash_probe() without setting 'cxlflash_cfg->state' to STATE_PROBED and the probe thread starts to wait on 'cxlflash_cfg->reset_waitq'. Since the device was never successfully probed the 'cxlflash_cfg->state' never changes from STATE_PROBING hence the deadlock occurs.

We fix this deadlock by setting the variable 'cxlflash_cfg->state' to STATE_PROBED in case an error occurs during cxlflash_probe() and just before calling cxlflash_remove().

Cc: stable@vger.kernel.org Fixes: c21e0bbfc485("cxlflash: Base support for IBM CXL Flash Adapter") Signed-off-by: Vaibhav Jain vaibhav@linux.ibm.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com

diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c index bfa13e3b191c..c8bad2c093b8 100644 --- a/drivers/scsi/cxlflash/main.c +++ b/drivers/scsi/cxlflash/main.c @@ -3687,6 +3687,7 @@ static int cxlflash_probe(struct pci_dev *pdev, host->max_cmd_len = CXLFLASH_MAX_CDB_LEN;

cfg = shost_priv(host); + cfg->state = STATE_PROBING; cfg->host = host; rc = alloc_mem(cfg); if (rc) { @@ -3775,6 +3776,7 @@ static int cxlflash_probe(struct pci_dev *pdev, return rc;

out_remove: + cfg->state = STATE_PROBED; cxlflash_remove(pdev); goto out; }